1. Field of the Invention
The present invention relates generally to an automatic automotive transmission and more specifically to a clutch drum for a planetary gear unit of such a transmission.
2. Description of the Prior Art
In a previously proposed arrangement, such as shown in FIG. 1 of the drawings, a clutch drum 100 has been manufactured via press forming. In this arrangement, the plurality of corrugations 101 define both internal and external spline teeth which mount a plurality of clutch discs 102,103 on the exterior and in the interior thereof. This arrangement while being light in weight has suffered from the drawback of requiring a degree of precision during manufacture which renders mass production thereof excessively expensive.
As a solution to this it has been proposed to press form an arrangement such as shown in FIG. 2 of the drawings. In this arrangement a plurality of slots 104 define elongate castle-like fingers 105 about the end of the drum 106 which serve as spline teeth for mounting clutch discs on the exterior and within the interior of the drum. However, this arrangement has suffered from the drawback that the sheet from which the drum is pressed must be adequately thick so as to endow on the elongate fingers 105 the required structural strength to withstand the inevitable torque variations. This of course increases the weight of the drum and further requires more power when pressing due to the gauge or thickness of the sheet metal.